Volcanic Activity Summary: AVO is lowering the Aviation Color Code to Yellow and the Alert Level to Advisory at Redoubt volcano. Seismic, satellite, gas, and deformation observations over the past few weeks indicate that growth of the lava dome at Redoubt has significantly slowed, if not stopped, and therefore it is possible that the current eruptive activity has ended. However, it is unknown if this represents the end of the 2009 eruption of Redoubt or if the activity has only paused temporarily and might resume in the next months.

The large lava dome located at the north side of the summit crater, and extending down the Drift Glacier Gorge, still presents a hazard. It is possible that this large mass of fresh lava is unstable and could fail with little or no warning, leading to significant ash production and possible lahars in the Drift River valley.

AVO will continue to monitor Redoubt's activity closely, but begin to transition off 24/7 staffing. Later updates will describe operational changes as they occur.

Remarks: The 2009 eruption of Redoubt volcano began March 15th, 2009 with a steam explosion. Between March 22nd and April 4th, Redoubt produced multiple significant explosions that sent ash and gas clouds to as high as 65,000 feet (19.8 km) above sea level that significantly disrupted air traffic and resulted in minor or trace amounts of ash in the city of Anchorage and other nearby communities. Voluminous mudflows inundated the Drift River Valley as far as Cook Inlet on March 23 and April 4. After April 4th, the eruption continued with extrusion of a lava dome within the summit crater, eventually producing a blocky lava flow that currently extends ~0.6 miles (1 km) down the north flank of the volcano.

Heavily ice-mantled Redoubt volcano is located on the western side of Cook Inlet, 170 km (106 mi) southwest of Anchorage and 82 km (51 mi) west of Kenai, within Lake Clark National Park. Redoubt is a stratovolcano that rises to 10,197 feet above sea level. Recent eruptions occurred in 1902, 1966-68, 1989-90, and 2009.

Next Notice: A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted athttp://www.avo.alaska.edu

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)

(2) Issued:

(20090630/1820Z)

(3) Volcano:

Redoubt (CAVW# 1103-03-)

(4) Current Color Code:

YELLOW

(5) Previous Color Code:

orange

(6) Source:

Alaska Volcano Observatory

(7) Notice Number:

2009/A41

(8) Volcano Location:

N 60 deg 29 min W 152 deg 44 min

(9) Area:

Cook Inlet-South Central Alaska

(10) Summit Elevation:

10197 ft (3108 m)

(11) Volcanic Activity Summary:

AVO is lowering the Aviation Color Code to Yellow and the Alert Level to Advisory at Redoubt volcano. Seismic, satellite, gas, and deformation observations over the past few weeks indicate that growth of the lava dome at Redoubt has significantly slowed, if not stopped, and therefore it is possible that the current eruptive activity has ended. However, it is unknown if this represents the end of the 2009 eruption of Redoubt or if the activity has only paused temporarily and might resume in the next months.

The large lava dome located at the north side of the summit crater, and extending down the Drift Glacier Gorge, still presents a hazard. It is possible that this large mass of fresh lava is unstable and could fail with little or no warning, leading to significant ash production and possible lahars in the Drift River valley.

AVO will continue to monitor Redoubt's activity closely, but begin to transition off 24/7 staffing. Later updates will describe operational changes as they occur.

(12) Volcanic cloud height:

Nil

(13) Other volcanic cloud information:

Nil

(14) Remarks:

The 2009 eruption of Redoubt volcano began March 15th, 2009 with a steam explosion. Between March 22nd and April 4th, Redoubt produced multiple significant explosions that sent ash and gas clouds to as high as 65,000 feet (19.8 km) above sea level that significantly disrupted air traffic and resulted in minor or trace amounts of ash in the city of Anchorage and other nearby communities. Voluminous mudflows inundated the Drift River Valley as far as Cook Inlet on March 23 and April 4. After April 4th, the eruption continued with extrusion of a lava dome within the summit crater, eventually producing a blocky lava flow that currently extends ~0.6 miles (1 km) down the north flank of the volcano.

Heavily ice-mantled Redoubt volcano is located on the western side of Cook Inlet, 170 km (106 mi) southwest of Anchorage and 82 km (51 mi) west of Kenai, within Lake Clark National Park. Redoubt is a stratovolcano that rises to 10,197 feet above sea level. Recent eruptions occurred in 1902, 1966-68, 1989-90, and 2009.

A new VONA will be issued if conditions change significantly or alert levels are modified. While a VONA is in effect, regularly scheduled updates are posted athttp://www.avo.alaska.edu

VOLCANO ALERT LEVELS

NORMALVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

ADVISORYVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCHVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.

WARNINGHazardous eruption is imminent, underway, or suspected.

AVIATION COLOR CODES

GREENVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

YELLOWVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

ORANGEVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].

REDEruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].